Rh-Fe/Ca-Al2O3: A Unique Catalyst for CO-Free Hydrogen Production in Low Temperature Ethanol Steam Reforming

Low temperature ethanol steam reforming (ESR) was studied over a series of 1 wt% Rh-x % Fe catalysts with various Fe loading (x = 0-10 wt%) and on different supports (Ca-Al2O3, SiO2 and ZrO2). The results show that close interaction between Rh and Fe is required to reduce the CO selectivity to almost negligible values. In addition, Rh-Fe supported on Ca-Al2O3 exhibits the best performance in terms of CO selectivity and hydrogen yield as compared to other supports. Characterization by XPS and XANES indicates the presence of FexOy species upon reduction, resulting in the formation of coordinatively unsaturated ferrous (CUF) active sites along the Rh-FexOy interface. These CUF sites promote water-gas shift reaction during low temperature ESR. Temperature programmed oxidation and Raman spectroscopy of spent catalysts also indicate that the addition of iron oxide reduces coke deposition and forms more reactive coke. Hence, the catalyst lifespan is significantly extended.